1. Field of the Invention
The present invention relates to systems for measuring parameters with elongated waveguides in magnetostrictive displacement and liquid level or distance measuring transducers, and more particularly to controllers for control of the measured parameters.
2. Description of the Art
Magnetostrictive transducers having elongated waveguides that carry torsional strain waves induced in the waveguide when current pulses are applied along the waveguide through a magnetic field are well known in the art. A typical linear distance measuring device using a movable magnet that interacts with the waveguide when current pulses are provided along the waveguide is shown in U.S. Pat. No. 3,898,555. A preferred sensor element for such measurement is the SE2 sensor sold by MTS which includes a SARA measuring unit. The prior art also shows controllers and regulators that control, including locally, a measured signal, the local controllers being analog electrical or pneumatic or hydraulic systems.
Absolute encoders and linear transducers with incremental interfaces are also known in the art, such as those produced by TR Encoder Solutions.
No controllers of the prior art are close coupled to magnetostrictive devices and inside a magnetostrictive device cover. No controllers of the prior art run at one millisecond or better rates, such as one-half millisecond, on a digital basis calculating control changes.
It is an object of the present invention to provide digital magnetostrictive position sensing elements that can be used in digital control applications with analog or digital output.
It is further object of the present invention to produce a magnetostrictive position sensor probe and controller close coupled for very fast data input, for example, used in machine control.
It is a further object of the present invention to produce a magnetostrictive position sensor probe and controller with very fast control cycles, such as one millisecond or less.
It is also an object of the present invention to produce a microcontroller.
The present invention relates to a control system for a magnetostrictive position sensing probe that can be used in applications where the waveguide measures a variable that needs to be controlled, for example, a machine tool with a magnetostrictive measuring parameter such as distance of extension of an arm. Distance measurements may be made to a magnet carried by the piston of an hydraulic cylinder. A controller using a magnetostrictive sensor is especially useful for control systems that require high frequency update, such as, a full new reading every millisecond. The controller also may accept direct digital inputs represented as a variable to be measured, thereby decreasing the conversion time from an analog to a digital signal. The control system may be used in magnetostrictive displacement applications, for linear measurements with any magnetostrictive sensing device known in the prior art or yet to be determined.
The controller may be used to drive servo valves or proportional valves or external driver assemblies or motion powered devices or servo motors or the like (xe2x80x9coutput devicesxe2x80x9d) and may also through its computer communicate through a serial port with programmable computers or programmable logic controllers or human interface devices and the like (xe2x80x9chierarchyxe2x80x9d). The controller may also be connected directly to parallel digital input such as the input from a SARA counter or from a serial input such as the encoder as is well known in the art. The controller includes a microprocessor having interrupts to use the serial port of the microprocesser to supply data in the hierarchy and to accept parameters for use in the control algorithms and the like and to accept targets or set points for the controller. The computer of the controller also includes interrupts for the real time clock or timer and finally has an interrupt when position data is available from systems such as the SARA. It can also receive serial port input data such as from an encoder. Thus, no particular magnetostrictive sensor will be described, but only depicted generally in the descriptions of the invention below, although the MTS SE2 magnetostrictive sensor, using a SARA counter, is the presently preferred device.
The controller is close-coupled to the magnetostrictive device, usually being inside the cap of the magnetostrictive device, and having a frequency of one millisecond and up, preferably under five hundred microseconds, especially because of the close-coupling. Thus, the controller is microsized to permit it to be included within the normal housing of the magnetostrictive device.